The moisture content of freshly harvested grain is generally too high for immediate storage and must be lowered to prevent spoilage. A moisture content of 14-15% is considered acceptable for most grain elevator operators. The removal of too much moisture is, however, wasteful of drying energy and usually results in shrinkage which decreases the sale value of the grain.
There are a number of types of grain dryers in current use of which two major types are the continuous flow type and the batch type. In the continuous flow type there is generally large volumes of air at a relatively high temperature passed through the grain in a drying chamber with heat damage being minimized by a short stay of grain in the chamber. Continuous flow dryers are generally classed as concurrent flow, cross flow and counter flow depending on the relationship between the directions of grain flow and air flow through the drying chamber. Continuous flow grain drying is capable of high rates of grain processing; however, the energy efficiency of such drying in most cases is not optimum because the drying air does not become saturated with moisture because of the high flow rate of the drying air.
To obviate the problems of the continuous flow dryer the applicant has improved the batch type grain dryer. The batch type dryer has a drying bin with a quantity of grain placed therein and heated air passed therethrough until the grain is dryed. To prevent overdrying of the lower layer applicant has recirculated the grain to the upper area of the bin and has improved on the air flow and grain flow to increase the efficiency and uniformity of drying. Overdrying resulting in the cracking of the kernels and the lowering of the quality of the grain has been overcome.
Attempts at improving grain drying have been made as disclosed in Canadian Patent 950,660, in U.K. Patent application 2,105,449 and in U.S. Pat. No. 3,824,705. In regard to patent "660" there is taught a concurrent countercurrent dryer with upper transverse heated inlet ducts and lower transverse exhaust ducts. Also shown are cold inlet ducts. While applicant has heated upper ducts and lower exhaust ducts it further includes recirculating auger means, a central circular plenum hot air delivery, improved grain flow means and alternate hot air flow not found in the reference. In regard to published application "449" there is again shown an upper hot air inlet and lower hot air outlet. This is a continuous flow apparatus and is entirely different to applicants recirculating batch type with a recirculating auger, central hot air plenum and improved grain flow means. In regard to U.S. Pat. No. "705", there is shown a continuous counterflow grain drying system. Applicant has provided for a recirculating batch type with concurrent or countercurrent flow of hot air for drying.
None of the above patents either singely or combined teach or even suggest applicants new and improved grain dryer.